U.S. patent application number 15/789282 was filed with the patent office on 2018-02-08 for methods of etching films comprising transition metals.
The applicant listed for this patent is Applied Materials, Inc.. Invention is credited to Jeffrey W. Anthis, Benjamin Schmiege, David Thompson.
Application Number | 20180040486 15/789282 |
Document ID | / |
Family ID | 51528996 |
Filed Date | 2018-02-08 |
United States Patent
Application |
20180040486 |
Kind Code |
A1 |
Anthis; Jeffrey W. ; et
al. |
February 8, 2018 |
Methods Of Etching Films Comprising Transition Metals
Abstract
Provided are methods for etching films comprising transition
metals. Certain methods involve activating a substrate surface
comprising at least one transition metal, wherein activation of the
substrate surface comprises exposing the substrate surface to heat,
a plasma, an oxidizing environment, or a halide transfer agent to
provide an activated substrate surface; and exposing the activated
substrate surface to a reagent comprising a Lewis base or pi acid
to provide a vapor phase coordination complex comprising one or
more atoms of the transition metal coordinated to one or more
ligands from the reagent. Certain other methods provide selective
etching from a multi-layer substrate comprising two or more of a
layer of Co, a layer of Cu and a layer of Ni.
Inventors: |
Anthis; Jeffrey W.; (San
Jose, CA) ; Schmiege; Benjamin; (Santa Clara, CA)
; Thompson; David; (San Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Applied Materials, Inc. |
Santa Clara |
CA |
US |
|
|
Family ID: |
51528996 |
Appl. No.: |
15/789282 |
Filed: |
October 20, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15177726 |
Jun 9, 2016 |
9799533 |
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15789282 |
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14206474 |
Mar 12, 2014 |
9390940 |
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15177726 |
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61779583 |
Mar 13, 2013 |
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61892186 |
Oct 17, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01J 37/32715 20130101;
H01L 21/32135 20130101; C23F 1/12 20130101; C23F 4/00 20130101;
C23F 1/00 20130101; H01L 21/32136 20130101; H01J 37/32862
20130101 |
International
Class: |
H01L 21/3213 20060101
H01L021/3213; C23F 4/00 20060101 C23F004/00; C23F 1/00 20060101
C23F001/00; C23F 1/12 20060101 C23F001/12; H01J 37/32 20060101
H01J037/32 |
Claims
1. A method of etching a substrate, the method comprising:
activating a substrate surface comprising a transition metal,
wherein activation of the substrate surface comprises exposing the
substrate surface to a halide transfer agent to provide an
activated substrate surface; and exposing the activated substrate
surface to a reagent comprising a Lewis base or pi acid to provide
a vapor phase coordination complex comprising one or more atoms of
the transition metal coordinated to one or more ligands from the
reagent wherein the Lewis base or pi acid comprises one or more of
1,2-bis(difluorophosphino)ethane or a compound having the
structure: ##STR00006## wherein each R.sup.b is independently
hydrogen or C1-C4 alkyl.
2. The method of claim 1, wherein the Lewis base or pi acid
comprises a compound having the structure represented by:
##STR00007## wherein each R is independently hydrogen or C1-C4
alkyl group with the proviso that not all of the R groups are
hydrogen.
3. The method of claim 1, wherein exposure of the substrate surface
to the halide transfer agent and the reagent occur sequentially or
substantially sequentially.
4. The method of claim 1, wherein the plasma comprises N.sub.2O,
and exposure of the substrate surface to the N.sub.2O results in a
--NO surface termination.
5. The method of claim 1, wherein the transition metal comprises an
element selected from the group consisting of Co, Cu, Ru, Ni, Fe,
Pt, Mn and Pd.
6. The method of claim 1, wherein the substrate surface comprises
about 90 to about 100% transition metal and 0 to about 10%
carbon.
7. The method of claim 1, wherein the substrate surface overlies a
deposition chamber wall or showerhead.
8. A method of etching a substrate, the method comprising:
activating a substrate surface comprising a transition metal,
wherein activation of the substrate surface comprises exposing the
substrate surface to heat, a plasma, or an oxidizing environment to
provide an activated substrate surface; and exposing the activated
substrate surface to a reagent comprising a Lewis base or pi acid
to provide a vapor phase coordination complex comprising one or
more atoms of the transition metal coordinated to one or more
ligands from the reagent wherein the Lewis base or pi acid
comprises one or more of 1,2-bis(difluorophosphino)ethane or a
compound having the structure: ##STR00008## wherein each R.sup.b is
independently hydrogen or C1-C4 alkyl.
9. The method of claim 8, wherein the Lewis base or pi acid
comprises a structure represented by: ##STR00009## wherein each R
is independently hydrogen or C1-C4 alkyl group with the proviso
that not all of the R groups are hydrogen.
10. The method of claim 8, wherein activation of the substrate
surface comprises exposing the substrate surface to heat.
11. The method of claim 8, wherein exposure of the substrate
surface to heat and the reagent occur sequentially or substantially
sequentially.
12. The method of claim 8, wherein activation of the substrate
surface comprises exposing the substrate surface to a plasma.
13. The method of claim 12, wherein the plasma comprises H.sub.2,
NO, N.sub.2O, NF.sub.3, Cl.sub.2, Ar or N.sub.2.
14. The method of claim 12, wherein the plasma comprises N.sub.2O,
and exposure of the substrate surface to the N.sub.2O results in a
--NO surface termination.
15. The method of claim 8, wherein exposure of the substrate
surface to an oxidizing environment comprises exposing the
substrate surface to O.sub.2, O.sub.3, N.sub.2O, NO, Br.sub.2,
F.sub.2, I.sub.2 or Cl.sub.2.
16. The method of claim 8, wherein the transition metal comprises
an element selected from the group consisting of Co, Ru, Ni, Fe,
Pt, Mn and Pd.
17. The method of claim 8, wherein the substrate surface comprises
about 90 to about 100% transition metal and 0 to about 10%
carbon.
18. The method of claim 8, wherein the substrate surface overlies a
deposition chamber wall or showerhead.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. Non-Provisional
application Ser. No. 15/177,726, filed Jun. 9, 2016, which is a
continuation of U.S. Non-Provisional application Ser. No.
14/206,474, filed Mar. 12, 2014, now U.S. Pat. No. 9,390,940, dated
Jul. 12, 2016, which claims priority to U.S. Provisional
Application Nos. 61/779,583, filed Mar. 13, 2013 and 61/892,186,
filed Oct. 17, 2013, the entire contents of each of which are
herein incorporated by reference in their entirety.
TECHNICAL FIELD
[0002] Aspects of the present invention relates generally to
methods of etching films. In particular, aspects of the invention
relates to etching films comprising transition metals for
semiconductor devices.
BACKGROUND
[0003] Deposition of films on a substrate surface is an important
process in a variety of industries including semiconductor
processing, diffusion barrier coatings and dielectrics for magnetic
read/write heads. Chemical vapor deposition (CVD) and atomic layer
deposition (ALD) are two deposition processes used to form or
deposit various materials on a substrate. In general, CVD and ALD
processes involve the delivery of gaseous reactants to the
substrate surface where a chemical reaction takes place under
temperature and pressure conditions favorable to the thermodynamics
of the reaction. However, a common problem with one or more these
deposition processes is the unwanted deposition onto deposition
chamber walls, showerhead, etc. For example, if cobalt films are
deposited, there is a possibility for the buildup of undesired
cobalt metal or compounds (e.g., carbidic cobalt) on the walls of
the chamber. It then becomes necessary to remove this buildup.
There is thus a need for methods of cleaning such buildup from
deposition equipment. In particular, it would be particularly
advantageous to have self-limiting etch methods, which would yield
greater control during etch.
[0004] Additionally, in the semiconductor industry, miniaturization
requires atomic level control of thin film deposition to produce
conformal coatings on high aspect structures. One method for
deposition of thin films with control and conformal deposition is
atomic layer deposition (ALD), which employs sequential, surface
reactions to form layers of precise thickness. Most ALD processes
are based on binary reaction sequences which deposit a binary
compound film. Because the surface reactions are sequential, the
two gas phase reactants are not in contact, and possible gas phase
reactions that may form and deposit particles are limited. However,
before the present invention, there has not been a commercially
viable way to delicately etch films with control and conformality.
For example, while there have been wet etch methods proposed for
cobalt, there is still a need for dry methods to remove cobalt
and/or cobalt residue, and preferably in situ methods that are
self-limiting and allow for precise control over etch rate. Even
more particularly, a method that is selective for a particular
metal is desired, as it would provide even more control over the
etching process.
SUMMARY
[0005] One aspect of the invention pertains to a method of etching
a substrate. the method comprises activating a substrate surface
comprising at least one transition metal, wherein activation of the
substrate surface comprises exposing the substrate surface to heat,
a plasma, an oxidizing environment, or a halide transfer agent to
provide an activated substrate surface; and exposing the activated
substrate surface to a reagent comprising a Lewis base or pi acid
to provide a vapor phase coordination complex comprising one or
more atoms of the transition metal coordinated to one or more
ligands from the reagent.
[0006] In one or more embodiments, the Lewis base or pi acid
comprises CO, PR.sup.1.sub.3, wherein each R.sup.1 is independently
a C1-C6 alkyl group, 1,2-bis(difluorophosphino)ethane, N.sub.2O,
NO, NH.sub.3, NR.sup.2.sub.3, wherein each R.sup.2 is independently
hydrogen C1-C6 branched or unbranched, substituted or
unsubstituted, alkyl, allyl or cyclic hydrocarbon or heteroatomic
group, or a compound having the structure:
##STR00001##
[0007] wherein each R.sup.b is independently hydrogen, R or C1-C4
alkyl. In some embodiments, the pi acid comprises
AlH.sub.nX.sub.mR.sup.c.sub.p, wherein X is a halogen, the sum of
n+m+p is 3, and R.sup.c is C1-C6 alkyl. In one or more embodiments,
activation of the substrate surface provides a surface termination
which will react with a Lewis acid and/or pi acid. In some
embodiments, the Lewis base or pi acid comprises a chelating amine
selected from the group consisting of N,N,N',N'-tetramethylethylene
diamine, ethylene diamine, N,N'-dimethylethylenediamine,
2-(aminomethyl)pyridine, 2-[(alkylamino)methyl]pyridine, and
2-[(dialkylamino)methyl]pyridine, wherein the alkyl group is C1-C6
alkyl.
[0008] The activation of the substrate surface can take several
forms. In one or more embodiments, activation of the substrate
surface comprises exposing the substrate surface to heat. In some
embodiments, exposure of the substrate surface to heat and the
reagent occur simultaneously or substantially simultaneously.
[0009] In one or more embodiments, activation of the substrate
surface comprises exposing the substrate surface to a plasma. In
some embodiments, exposure of the substrate surface to the plasma
and the reagent occur simultaneously or substantially
simultaneously. In further embodiments, the plasma comprises
H.sub.2, NO, N.sub.2O, NF.sub.3, Cl.sub.2, Ar or N.sub.2. In one or
more embodiments, the plasma comprises N.sub.2O, and exposure of
the substrate surface to the N.sub.2O results in a --NO surface
termination.
[0010] In some embodiments, activation of the substrate surface
comprises exposure to a halide transfer agent. In further
embodiments, the halide transfer agent comprises I.sub.2, Br.sub.2,
Cl.sub.2, a trialkylsilyl halide or an alkyl halide, wherein the
alkyl group may be C1-C6 alkyl.
[0011] In one or more embodiments, activation of the substrate
surface comprises exposure of the substrate surface to an oxidizing
environment. In further embodiments, exposure of the substrate
surface to an oxidizing environment comprises exposing the
substrate surface to O.sub.2, O.sub.3, N.sub.2O, NO, Br.sub.2,
F.sub.2, I.sub.2 or Cl.sub.2.
[0012] In some embodiments, the transition metal comprises an
element selected from the group consisting of Co, Cu, Ru, Ni, Fe,
Pt, Mn and Pd. In one or more embodiments, the substrate surface
comprises about 90 to about 100% transition metal and 0 to about
10% carbon.
[0013] There are also other variants of the method. In one or more
embodiments, the substrate surface overlies a deposition chamber
wall or showerhead. In some embodiments, the method further
comprises purging the vapor phase coordination complex.
[0014] A second aspect of the invention pertains to a method of
etching a multi-layer substrate. The method comprises providing a
multi-layer substrate comprising two or more of a layer of Co, a
layer of Cu and a layer of Ni; activating a surface of the layer of
Co, layer of Cu or layer of Ni, wherein activation of the substrate
surface comprises exposing the substrate surface to heat, a plasma
or a halide transfer agent to provide an activated substrate
surface; and exposing the activated substrate surface to a
chelating amine at a first temperature such that the chelating
amine will only form a volatile metal coordination complex with one
of Co, Cu or Ni at the first temperature.
[0015] In one or more embodiments, the method further comprises
exposing the activated substrate surface to a chelating amine at a
second temperature, such that the chelating amine will only form a
volatile metal coordination complex with one of Co, Cu or Ni at the
second temperature. In some embodiments, the chelating amine has a
structure represented by:
##STR00002##
[0016] wherein each R.sup.a is independently hydrogen or C1-C4
alkyl, with the proviso that not all of the R.sup.a groups are
hydrogen. In some embodiments, the chelating amine is selected from
the group consisting of N,N,N',N'-tetramethylethylene diamine and
N,N'-dimethylethylenediamine. In one or more embodiments, the
method further comprises purging the coordination complex.
[0017] A third aspect of the invention pertains to a method of
etching a substrate, the method comprising: activating a substrate
surface comprising cobalt or copper, wherein activation of the
substrate surface comprises exposing the substrate surface to
Br.sub.2 to provide an activated substrate surface; and exposing
the activated substrate surface to a reagent comprising TMEDA to
provide a vapor phase coordination complex comprising one or more
atoms of the cobalt or copper coordinated to one or more ligands
from the reagent.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] So that the manner in which the above recited features of
the present invention can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0019] FIG. 1 shows a schematic of a method in accordance with one
or more embodiments of the invention;
[0020] FIG. 2 shows a schematic of a method in accordance with one
or more embodiments of the invention;
[0021] FIG. 3 shows a schematic of a method in accordance with one
or more embodiments of the invention;
[0022] FIG. 4 shows a schematic of a method in accordance with one
or more embodiments of the invention;
[0023] FIG. 5 shows a schematic of a method in accordance with one
or more embodiments of the invention;
[0024] FIG. 6 shows a graph of amount of cobalt etched as a
function of cycles for a process in accordance with one or more
embodiments of the invention;
[0025] FIG. 7 shows a schematic of a method in accordance with one
or more embodiments of the invention;
[0026] FIG. 8 shows a graph of the amount of cobalt etched as a
function of temperature for a process in accordance with one or
more embodiments of the invention;
[0027] FIG. 9 shows a graph of the amount of cobalt etched as a
function of temperature for a process in accordance with one or
more embodiments of the invention; and
[0028] FIG. 10 shows a schematic of a method in accordance with one
or more embodiments of the invention.
DETAILED DESCRIPTION
[0029] Before describing several exemplary embodiments of the
invention, it is to be understood that the invention is not limited
to the details of construction or process steps set forth in the
following description. The invention is capable of other
embodiments and of being practiced or being carried out in various
ways. It is also to be understood that the complexes and ligands of
the present invention may be illustrated herein using structural
formulas which have a particular stereochemistry. These
illustrations are intended as examples only and are not to be
construed as limiting the disclosed structure to any particular
stereochemistry. Rather, the illustrated structures are intended to
encompass all such complexes and ligands having the indicated
chemical formula.
[0030] It has been discovered that certain combinations of
activation methods and reagents allow for the etching of substrates
comprising at least one transition metal. Possible methods for the
activation of a substrate surface include exposing the substrate
surface to heat, a plasma, an oxidizing environment, or a halide
transfer agent. Reagents include Lewis bases and/or pi acids. These
processes allow for the formation of volatile metal coordination
complexes of the substrate metal, which can then be flowed away or
purged from the substrate surface, thereby removing some of the
substrate. Certain processes relate to selective metal etching,
which allow for removal of one transition metal, while leaving
another intact.
[0031] Accordingly, one aspect of the invention pertains to a
method of etching a substrate. The method comprises activating a
substrate surface comprising at least one transition metal.
Activation of the substrate surface comprises exposing the
substrate surface to heat, a plasma, an oxidizing environment, or a
halide transfer agent to provide an activated substrate surface;
and exposing the activated substrate surface to a reagent
comprising a Lewis base or pi acid to provide a vapor phase
coordination complex comprising one or more atoms of the transition
metal coordinated to one or more ligands from the reagent.
[0032] A "substrate" as used herein broadly covers substrates
comprising one or more transition metals. In some embodiments, the
term includes equipment that has a layer of buildup deposited
thereon. As described above, a common problem with one or more of
these deposition processes is the unwanted deposition onto
deposition chamber walls, showerhead, etc. Thus, in some
embodiments, the substrate comprises deposited metal overlying a
deposition chamber wall, a deposition showerhead, etc. In one or
more embodiments, the term refers to any substrate or material
surface comprising a transition metal that is formed on a second
substrate upon which film processing is performed during a
fabrication process. Substrates may be exposed to a pretreatment
process to polish, etch, reduce, oxidize, hydroxylate, anneal
and/or bake the substrate surface. The term "substrate surface"
refers to an exposed surface of the substrate. In one or more
embodiments, and as the context dictates, as layers are added to
the substrate or (in the alternative) part of the substrate is
removed, the newly exposed surface becomes the substrate
surface.
[0033] In one or more embodiments, the substrate surface comprises
at least one transition metal. In one or more embodiments, the
transition metal comprises a first row transition metal. In some
embodiments, the transition metal is selected from the group
consisting of Co, Cu, Ru, Ni, Fe, Pt, Mn and Pd. In some
embodiments, the substrate surface consists essentially of the
transition metal. In one or more embodiments, the substrate surface
may comprise more than one transition metal, including metal
alloys. An example of such a substrate includes a substrate
comprising both cobalt and iron.
[0034] In other embodiments, the substrate surface comprises at
least one transition metal, but also comprises other components.
Other components may include carbon. In one or more embodiments,
the substrate surface comprises about 90 to about 100% transition
metal and 0 to about 10% carbon. Carbide films may be especially
seen in embodiments relating to the removal of transition metal
carbides deposited onto deposition chamber walls, showerheads, and
other equipment components. In some embodiments, the other
components may include oxygen, boron, sulfur and/or nitrogen.
Therefore, other examples of suitable substrate comprise materials
include metal alloys/intermetallics, metal oxides, metal borides,
metal sulfides, metal nitrides, metal intermetallic borides, metal
intermetallic oxides, metal intermetallic sulfides and metal
intermetallic nitrides. To be clear, the above encompasses
substrate comprising more than one transition metal as well as
additional components. An example of such a material is a substrate
comprising cobalt, iron and boron (CoFeB).
[0035] Once the surface has been activated and a reagent gas has
been flowed over the reactive surface, it is thought that the
reagent gas forms a metal coordination complex with one or more of
the transition metal atoms from the substrate surface. Ideally, the
reaction conditions are chosen so that the formed coordination
complex is volatile at a given temperature (i.e., in the vapor
phase). Then, the complex may simply be flowed away from the
substrate surface and, as appropriate, out of the chamber. That is,
in some embodiments, the method further comprises purging the vapor
phase coordination complex.
[0036] The substrate surface will therefore be at least one metal
layer thinner than before the etch process. In some embodiments,
the etch process is self-limiting. That is, each time an etch cycle
is performed, the same amount of the substrate is removed, although
not necessarily at the monolayer. For example, a certain number of
Angstroms (e.g., about 7), or several monolayers may be removed per
cycle. In these embodiments, one or more layers of transition metal
atoms may be reliably removed each cycle. Such a method may be
referred to as "alternating exposure etching," where the substrate
surface is sequentially or substantially sequentially exposed to
reagent and activation agents. As used herein "substantially
sequentially" means that the majority of the duration of the pulses
does not overlap with the pulse of co-reagent, although there may
be some overlap. In other embodiments, the process may be
self-limiting at the monolayer. That is, in such embodiments, only
one layer of transition metal atoms is removed at a time. Such a
process may be referred to as "atomic layer etching."
[0037] The specific reaction conditions for the etch reactions may
be selected based on the properties of the reagents and substrate
surface, as well as the pressure used. The etch may be carried out
at atmospheric pressure, but may also be carried out at reduced
pressure. The substrate temperature should be high enough to keep
the formed metal complexes in the gaseous phase and to provide
sufficient energy for surface reactions. The properties of the
specific substrate, film precursors, etc. may be evaluated using
methods known in the art, allowing selection of appropriate
temperature and pressure for the reaction.
[0038] In some embodiments, the substrate surface temperature is
kept below about 500, 475, 450, 425, 400, 375, 350, 325, or
300.degree. C. In embodiments where the etch is utilized for
cleaning buildup off of equipment, the substrate temperature may be
kept below 250, 225, or 200.degree. C. The substrate surface
temperature should be at least about room temperature (23.degree.
C.) or at least about 25, 50 or 75.degree. C.
Reagents
[0039] In accordance with one or more embodiments of the invention,
the reagents comprise a Lewis base or pi acid. A "pi acid," as used
herein, refers to a compound that, as a ligand, can accept electron
density from a metal into empty pi orbitals as well as donate
electron density to the metal via a sigma bond. A "Lewis base," as
used herein, refers to a compound that, as a ligand, can donate an
electron pair to a metal. There are several suitable reagents for
the processes described herein.
[0040] In one or more embodiments, the Lewis base or pi acid
comprises a chelating amine. In some embodiments, the chelating
amine has a structure represented by:
##STR00003##
wherein each R.sup.a is independently hydrogen or C1-C4 alkyl group
with the proviso that not all of the R.sup.a groups are hydrogen.
In further embodiments, the chelating amine is selected from the
group consisting of N,N,N',N'-tetramethylethylene diamine (also
known as TMEDA), ethylene diamine, N,N'-dimethylethylenediamine,
2-(aminomethyl)pyridine, 2-[(alkylamino)methyl]pyridine, and
2-[(dialkylamino)methyl]pyridine, wherein the alkyl group is a
C1-C6 alkyl group.
[0041] In some embodiments, the Lewis base or pi acid comprises CO,
alkylphosphines (PR.sup.1.sub.3, wherein each R.sup.1 is a C1-C6
alkyl group), 1,2-bis(difluorophosphino)ethane, N.sub.2O, NO,
NH.sub.3, NR.sup.2.sub.3, wherein each R.sup.2 is independently
hydrogen or C1-C6 branched or unbranched, substituted or
unsubstituted, alkyl, allyl or cyclic hydrocarbon or heteroatomic
group, or a compound having the structure:
##STR00004##
wherein each R.sup.b is independently hydrogen, R or C1-C4 alkyl.
It is noted that N.sub.2O is not a traditional Lewis base, but does
have a lone electron pair. In some embodiments, wherein the reagent
comprises NR.sup.2.sub.3, each R.sup.2 is independently C1-C6
alkyl. In other embodiments, at least one of the R.sup.2 groups is
cyclohexylamine.
[0042] In one or more embodiments, the pi acid comprises an
aluminum precursor. In further embodiments, the aluminum precursor
has formula AlH.sub.nX.sub.mR.sup.c.sub.p, wherein X is a halogen,
the sum of n+m+p is 3, and R.sup.c is C1-C6 alkyl.
Activation
[0043] In one or more embodiments, the process includes activation
of the substrate surface. In some embodiments, activation of the
substrate surface provides a surface termination which will react
with a Lewis acid and/or pi acid. In further embodiments, the
surface termination will react with any one or more of the Lewis
acids and/or pi acids.
[0044] In some embodiments, activation of the substrate surface is
accomplished by heating the substrate surface. Heating the
substrate surface can be carried out by methods known in the art,
including simply heating the chamber. In some embodiments, the
substrate surface temperature is kept below about 400, 375, 350,
325, or 300.degree. C. In embodiments where the etch is utilized
for cleaning buildup off of equipment, the substrate temperature
may be kept below 250, 225, or 200.degree. C. The substrate surface
temperature should be at least about room temperature (23.degree.
C.) or at least about 25, 50 or 75.degree. C.
[0045] With processes that include heating, a reagent gas may be
passed over the heated substrate. The substrate surface may be
heated and exposed to the reagent gas simultaneously or
substantially simultaneously. As used herein, the phrase "exposure
of the substrate surface to heat and the reagent occur
substantially simultaneously" means that the substrate surface is
heated with a majority of the heating duration overlapping with
exposure to the reagent, although they might not be completely
co-extensive. In some embodiments, the reagent gas utilized after
heating the substrate comprises one or more of CO, PR.sup.1.sub.3,
N.sub.2O, NO, NH.sub.3, NR.sup.2.sub.3, wherein each R.sup.1 is a
C1-C6 alkyl group and each R.sup.2 is C1-C6 branched or unbranched,
substituted or unsubstituted, alkyl, allyl or cyclic hydrocarbon or
heteroatomic group. In other embodiments, the reagent gas comprises
a chelating amine, such as N,N,N'N'-tetramethylethylene diamine and
N,N'-dimethylethylenediamine.
[0046] In some embodiments, activation of the substrate surface
comprises exposing the substrate surface to a plasma. The substrate
surface may be exposed to the plasma and the reagent gas
sequentially, substantially sequentially, simultaneously or
substantially simultaneously. As used herein, the phrase "exposure
of the substrate surface to the plasma and the reagent occur
substantially sequentially" means that the substrate surface is
exposed to the plasma with a majority of the plasma exposure
duration not coinciding with exposure to the reagent, although
there may be some overlap. As used herein, the phrase "exposure of
the substrate surface to the plasma and the reagent occur
substantially simultaneously" means that the substrate surface is
exposed to the plasma with a majority of the plasma exposure
duration overlapping with exposure to the reagent, although they
might not be completely co-extensive.
[0047] Generally, a plasma used for activation should enhance the
reactivity of the surface toward subsequent reagent exposure steps.
In one or more embodiments, the plasma comprises H.sub.2, NO,
N.sub.2O, NF.sub.3, Cl.sub.2, Ar or N.sub.2. In some embodiments,
the plasma changes the substrate surface by adding a different
surface termination. For example, in embodiments where the
substrate surface is exposed to a plasma comprising N.sub.2O, the
exposure to the plasma is thought result in a --NO surface
termination. While not wishing to be bound to any particular
theory, it is thought that by adding such functionality, the
substrate surface becomes more reactive to certain reagents,
particularly one or more of the pi acids and/or Lewis bases
described herein.
[0048] In some embodiments, exposure to the substrate surface
comprises exposing the substrate surface to a halide transfer
agent. In one or more embodiments, exposure of the substrate
surface to the halide transfer agent and any pi acid and/or Lewis
base occurs sequentially or substantially sequentially As used
herein, the phrase "exposure of the substrate surface to the halide
transfer agent and the reagent occur substantially sequentially"
means that the substrate surface is exposed to the halide transfer
agent with a majority of the halide transfer agent exposure
duration not coinciding with exposure to the reagent, although
there may be some overlap. In some embodiments, exposure of the
substrate surface to the halide transfer agent and any pi acid
and/or Lewis base occurs simultaneously or substantially
simultaneously. As used herein, "substantially simultaneously"
means that the substrate surface is exposed to the halide transfer
agent with a majority of the halide transfer agent exposure
duration coinciding with exposure to the reagent, although there
may be some time where the two do not overlap. Again, while not
wishing to be bound to any particular theory, it is thought that
exposure of the substrate surface to a halide transfer agent
results in the substrate surface having halide surface
terminations, thereby making it more reactive to one or more of the
pi acids and/or Lewis bases described herein. In some embodiments,
the halide transfer agent comprises a dihalide. In further
embodiments, the dihalide comprises I.sub.2, Br.sub.2, Cl.sub.2. In
other embodiments, the halide transfer agent comprises a
trialkylsilyl halide or an alkyl halide, wherein the alkyl group(s)
of either the trialkylsilyl halide or alkyl halide may be a C1-C6
alkyl group. Examples of suitable alkyl halides include ethyliodide
and diiodoethane.
[0049] In some embodiments, activation of the substrate surface
comprises exposing the substrate surface to an oxidizing
environment. In one or more embodiments, exposure of the substrate
surface to the halide transfer agent and any pi acid and/or Lewis
base occurs sequentially or substantially sequentially. As used
herein, the phrase "exposure of the substrate surface to the
oxidizing environment and the reagent occur substantially
sequentially" means that the substrate surface is exposed to the
oxidizing environment with a majority of the oxidizing environment
exposure duration not coinciding with exposure to the reagent,
although there may be some overlap. In one or more embodiments,
exposure to an oxidizing environment comprises exposing the
substrate surface to O.sub.2, O.sub.3, N.sub.2O, NO, Br.sub.2,
F.sub.2, I.sub.2 or Cl.sub.2.
[0050] In some embodiments, the reagent gas utilized after exposing
the substrate to an oxidizing environment comprises one or more of
CO, PR.sup.1.sub.3, N.sub.2O, NO, NH.sub.3, NR.sup.2.sub.3, wherein
each R.sup.1 is a C1-C6 alkyl group and each R.sup.2 is C1-C6
branched or unbranched, substituted or unsubstituted, alkyl, allyl
or cyclic hydrocarbon or heteroatomic group. In other embodiments,
the reagent gas comprises a chelating amine, such as
N,N,N'N'-tetramethylethylene diamine and
N,N'-dimethylethylenediamine. In other embodiments, the reagent gas
utilized after exposing the substrate to an oxidizing surface
comprises an aluminum-containing precursor, such as
chloroalkylaluminums, aluminum trihalides, aluminum halide
hydrides, alkyl aluminum hydride.
[0051] It should be noted that any of the above activation
processes and/or reagents may be combined. That is, more than one
activation process may be utilized, or more than one reagent may be
used during a given etch sequence. Furthermore, it is to be
understood that the process may be repeated until the desired
amount of transition metal has been etched away.
Selective Etch Process
[0052] One or more of the processes described herein may be
utilized for selective etching. Accordingly, another aspect of the
invention relates to a method of etching a multi-layer substrate.
The method comprising providing a multi-layer substrate comprising
two or more of a layer of Co, a layer of Cu and a layer of Ni;
activating a surface of the layer of Co, layer of Cu or layer of
Ni, wherein activation of the substrate surface comprises exposing
the substrate surface to heat, a plasma or a halide transfer agent
to provide an activated substrate surface; and exposing the
activated substrate surface to a chelating amine at a first
temperature such that the chelating amine will only form a volatile
metal coordination complex with one of Co, Cu or Ni at the first
temperature. As discussed above, in one or more embodiments, the
multi-layer substrate may comprise another component selected from
the group consisting of oxygen, boron, carbon, sulfur, nitrogen,
and combinations thereof.
[0053] Generally, this process can be used to etch one of Co, Cu or
Ni at a time. That is, in one or more embodiments, Co can be
removed without disturbing Cu or Ni layers, Cu can be removed
without disturbing Co or Ni layers, and Ni can be removed without
disturbing Co or Cu layers. Once one of these layers is removed,
the temperature may be changed to remove a different metal. Thus,
in some embodiments, the method further comprises exposing the
activated substrate surface to a chelating amine at a second
temperature, such that the chelating amine will only form a
volatile metal coordination complex with one of Co, Cu or Ni at the
second temperature.
[0054] In some embodiments, the chelating amine has a structure
represented by:
##STR00005##
wherein each R.sup.a is independently H or C1-C4 alkyl, with the
proviso that not all of the R.sup.a groups are hydrogen. In one or
more embodiments, the chelating amine is selected from the group
consisting of N,N,N',N'-tetramethylethylene diamine and
N,N'-dimethylethylenediamine.
[0055] While not wishing to be bound to any particular theory, it
is thought that Ni, Co and Cu form coordination metal complexes
with the above chelating amine with different volatilities at
different temperatures. Thus, temperature may be controlled as a
parameter to complex one metal at a time, while leaving the other
two metals undisturbed. The specific temperatures will depend on
the specific metal and chelating amines selected.
Exemplary Processes
[0056] Several processes will be exemplified below and in the
figures. It is to be understood that the structures shown are
representative of the chemical mechanisms that are thought to be
occurring during the etch process. However, they are not intended
to be limiting, and other chemical structures may occur.
[0057] FIG. 1 illustrates an exemplary process in accordance with
one or more embodiments of the invention. Specifically, a thermal
etching process using halide activation and a Lewis base is shown.
First, a cobalt substrate surface is provided. The substrate
surface is exposed to a halide transfer agent. The halide transfer
agent may be a dihalide or an alkyl halide such as an ethyl halide.
An exemplary process may utilize Br.sub.2 at a substrate
temperature of at least about 200.degree. C.
[0058] Once the substrate surface is exposed to the halide transfer
agent, the surface is modified with halide termination/surface
functionality to provide an activated substrate surface. Next,
activated substrate surface is exposed to a Lewis base and/or pi
acid. FIG. 1 is shown with N,N,N',N'-tetramethylethylenediamine
(TMEDA) or a tertiary amine or a CO reagent. Once the activated
substrate surface is exposed to the reagent, the reagent complexes
a metal atom from the substrate surface. As shown in the process of
FIG. 1, where TMEDA is utilized as the reagent, it may complex a
cobalt atom, resulting in a metal coordination complex with the
cobalt coordinated to the N,N,N',N'-tetramethylethylenediamine and
two halide ligands. The formed cobalt complex may then be purged
away from the substrate surface, taking away at least one cobalt
atom from the original substrate surface.
[0059] FIG. 2 illustrates a process similar to FIG. 1, but instead
uses N,N'-dimethylethylenediamine and secondary amines, protonated
versions of TMEDA or tertiary amine respectively. A cobalt
substrate surface is again provided, and it is exposed to a halide
transfer agent to provide an activated surface. The activated
substrate surface is exposed to the N,N'-dimethylethylenediamine or
secondary amine reagent. The cobalt halide may act as a reactive
handle to generate cobalt amides in a metathesis reaction. With
these reagents, it is thought that the complexed cobalt will
contain two N,N'-dimethylethylenediamine or secondary amine
ligands, at least one of which would form a covalent bond with the
central metal atom. The other ligand is shown as forming a dative
bond. The process in FIG. 2 is shown having a hydrogen halide
byproduct. For example, where Br.sub.2 is used, HBr would be formed
as a byproduct. It is thought that a hydrogen halide byproduct
would help to increase the vapor pressure, so that the etch can be
carried out at a lower temperature.
[0060] FIG. 3 illustrates an etch process based on plasma
activation. A cobalt surface is again provided. The substrate
surface is exposed with a plasma (shown as H.sub.2), while
simultaneously exposed to a Lewis base (shown as either CO or
TMEDA). Once the activated substrate surface is exposed to the
reagent, the reagent complexes a metal atom from the substrate
surface. As shown in the process of FIG. 3, where CO is utilized as
the reagent, it may complex a cobalt atom, resulting in a metal
coordination complex with the cobalt coordinated to four CO
ligands. The formed cobalt complex may then be purged away from the
substrate surface, taking away at least one cobalt atom from the
original substrate surface.
[0061] FIG. 4 illustrates another etch process based on plasma
activation. In this process, a cobalt substrate surface is exposed
to a N.sub.2O plasma. The plasma activates the surface by creating
--NO functionality. The reagent, CO, is then used to complex the
cobalt, thought to result in a metal coordination complex having
the formula Co.sub.x(CO).sub.y(NO).sub.z. In one or more
embodiments, the complex may comprise a cobalt atom coordinated to
three CO ligands and one NO ligand, also known as
tetracarbonylcobalt nitrosyl. Tetracarbonylcobalt nitrosyl is known
to be quite volatile even at room temperature, which would allow
for etching at very low temperatures.
[0062] In some processes, the use of plasma provides sufficient
energy to promote a species into the excited state where surface
reactions become favorable and likely. Introducing the plasma into
the process can be continuous or pulsed. In some embodiments,
sequential pulses of precursors (or reactive gases) and plasma are
used to process a layer. In some embodiments, the reagents may be
ionized either locally (i.e., within the processing area) or
remotely (i.e., outside the processing area). In some embodiments,
remote ionization can occur upstream of the deposition chamber such
that ions or other energetic or light emitting species are not in
direct contact with the depositing film. In some PEALD processes,
the plasma is generated external from the processing chamber, such
as by a remote plasma generator system. The plasma may be generated
via any suitable plasma generation process or technique known to
those skilled in the art. For example, plasma may be generated by
one or more of a microwave (MW) frequency generator or a radio
frequency (RF) generator. The frequency of the plasma may be tuned
depending on the specific reactive species being used. Suitable
frequencies include, but are not limited to, 2 MHz, 13.56 MHz, 40
MHz, 60 MHz and 100 MHz. Although plasmas may be used during some
of the processes disclosed herein, it should be noted that plasmas
may not required.
[0063] One or more of the processes described herein include a
purge. The purging process keeps the reagents separate. The
substrate and chamber may be exposed to a purge step after stopping
the flow of one or more of the reagents. A purge gas may be
administered into the processing chamber with a flow rate within a
range from about 10 sccm to about 10,000 sccm, for example, from
about 50 sccm to about 5,000 sccm, and in a specific example, about
1000 sccm. The purge step removes any excess precursor, byproducts
and other contaminants within the processing chamber. The purge
step may be conducted for a time period within a range from about
0.1 seconds to about 60 seconds, for example, from about 1 second
to about 10 seconds, and in a specific example, from about 5
seconds. The carrier gas, the purge gas, the deposition gas, or
other process gas may contain nitrogen, hydrogen, argon, neon,
helium, or combinations thereof. In one example, the carrier gas
comprises argon and nitrogen.
[0064] According to one or more embodiments, the substrate is
subjected to processing prior to and/or after forming etch. This
processing can be performed in the same chamber or in one or more
separate processing chambers. In some embodiments, the substrate is
moved from the first chamber to a separate, second chamber for
further processing. The substrate can be moved directly from the
first chamber to the separate processing chamber, or it can be
moved from the first chamber to one or more transfer chambers, and
then moved to the desired separate processing chamber. Accordingly,
the processing apparatus may comprise multiple chambers in
communication with a transfer station. An apparatus of this sort
may be referred to as a "cluster tool" or "clustered system", and
the like.
[0065] Generally, a cluster tool is a modular system comprising
multiple chambers which perform various functions including
substrate center-finding and orientation, degassing, annealing,
deposition and/or etching. According to one or more embodiments, a
cluster tool includes at least a first chamber and a central
transfer chamber. The central transfer chamber may house a robot
that can shuttle substrates between and among processing chambers
and load lock chambers. The transfer chamber is typically
maintained at a vacuum condition and provides an intermediate stage
for shuttling substrates from one chamber to another and/or to a
load lock chamber positioned at a front end of the cluster tool.
Two well-known cluster tools which may be adapted for the present
invention are the Centura.RTM. and the Endura.RTM., both available
from Applied Materials, Inc., of Santa Clara, Calif. The details of
one such staged-vacuum substrate processing apparatus is disclosed
in U.S. Pat. No. 5,186,718, entitled "Staged-Vacuum Wafer
Processing Apparatus and Method," Tepman et al., issued on Feb. 16,
1993. However, the exact arrangement and combination of chambers
may be altered for purposes of performing specific steps of a
process as described herein. Other processing chambers which may be
used include, but are not limited to, cyclical layer deposition
(CLD), atomic layer deposition (ALD), chemical vapor deposition
(CVD), physical vapor deposition (PVD), other etch, pre-clean,
chemical clean, thermal treatment such as RTP, plasma nitridation,
degas, orientation, hydroxylation and other substrate processes. By
carrying out processes in a chamber on a cluster tool, surface
contamination of the substrate with atmospheric impurities can be
avoided without oxidation prior to depositing a subsequent
film.
[0066] According to one or more embodiments, the substrate is
continuously under vacuum or "load lock" conditions, and is not
exposed to ambient air when being moved from one chamber to the
next. The transfer chambers are thus under vacuum and are "pumped
down" under vacuum pressure. Inert gases may be present in the
processing chambers or the transfer chambers. In some embodiments,
an inert gas is used as a purge gas to remove some or all of the
reactants after forming the layer on the surface of the substrate.
According to one or more embodiments, a purge gas is injected at
the exit of the chamber to prevent reactants from moving from the
chamber to the transfer chamber and/or additional processing
chamber. Thus, the flow of inert gas forms a curtain at the exit of
the chamber.
[0067] The substrate can be processed in single substrate
deposition chambers, where a single substrate is loaded, processed
and unloaded before another substrate is processed. The substrate
can also be processed in a continuous manner, like a conveyer
system, in which multiple substrate are individually loaded into a
first part of the chamber, move through the chamber and are
unloaded from a second part of the chamber. The shape of the
chamber and associated conveyer system can form a straight path or
curved path. Additionally, the processing chamber may be a carousel
in which multiple substrates are moved about a central axis and are
exposed to deposition, etch, annealing, cleaning, etc. processes
throughout the carousel path.
[0068] During processing, the substrate can be heated or cooled.
Such heating or cooling can be accomplished by any suitable means
including, but not limited to, changing the temperature of the
substrate support and flowing heated or cooled gases to the
substrate surface. In some embodiments, the substrate support
includes a heater/cooler which can be controlled to change the
substrate temperature conductively. In one or more embodiments, the
gases (either reactive gases or inert gases) being employed are
heated or cooled to locally change the substrate temperature. In
some embodiments, a heater/cooler is positioned within the chamber
adjacent the substrate surface to convectively change the substrate
temperature.
[0069] The substrate can also be stationary or rotated during
processing. A rotating substrate can be rotated continuously or in
discreet steps. For example, a substrate may be rotated throughout
the entire process, or the substrate can be rotated by a small
amount between exposure to different reactive or purge gases.
Rotating the substrate during processing (either continuously or in
steps) may help produce a more uniform deposition or etch by
minimizing the effect of, for example, local variability in gas
flow geometries.
[0070] In atomic layer deposition-type chambers, the substrate can
be exposed to the reagents and/or other compounds either spatially
or temporally separated processes. Temporal ALD (or etch) is a
traditional process in which the first precursor flows into the
chamber to react with the surface. The first precursor is purged
from the chamber before flowing the second precursor. In spatial
ALD (or etch), both the first and second precursors are
simultaneously flowed to the chamber but are separated spatially so
that there is a region between the flows that prevents mixing of
the precursors. In spatial ALD, the substrate must be moved
relative to the gas distribution plate, or vice-versa.
[0071] Reference throughout this specification to "one embodiment,"
"certain embodiments," "one or more embodiments" or "an embodiment"
means that a particular feature, structure, material, or
characteristic described in connection with the embodiment is
included in at least one embodiment of the invention. Thus, the
appearances of the phrases such as "in one or more embodiments,"
"in certain embodiments," "in one embodiment" or "in an embodiment"
in various places throughout this specification are not necessarily
referring to the same embodiment of the invention. Furthermore, the
particular features, structures, materials, or characteristics may
be combined in any suitable manner in one or more embodiments.
[0072] Although the invention herein has been described with
reference to particular embodiments, it is to be understood that
these embodiments are merely illustrative of the principles and
applications of the present invention. It will be apparent to those
skilled in the art that various modifications and variations can be
made to the method and apparatus of the present invention without
departing from the spirit and scope of the invention. Thus, it is
intended that the present invention include modifications and
variations that are within the scope of the appended claims and
their equivalents.
Examples
Example 1--Cobalt Etch at 200-300.degree. C.
[0073] An air-exposed cobalt coupon deposited via plasma vapor
deposition (PVD) and having a thickness of 130 Angstroms was
provided. The cobalt coupon was deposited over a silicon substrate.
The cobalt coupon was exposed to 0.1 seconds of a Br.sub.2 pulse at
temperatures between 200 and 300.degree. C., followed by a 4 second
purge. The substrate surface was then exposed to a 1 second purge
of N,N,N',N'-tetramethylethylenediamine (TMEDA) at temperatures
between 200 and 300.degree. C., followed by another 4 second purge.
A possible chemical mechanism of this process is shown in FIG.
5.
[0074] After 20 cycles of Br.sub.2/TMEDA, all of the cobalt was
removed from the coupon, but the SiO.sub.2 was undisturbed, as
measured by X-Ray Fluorescence spectroscopy. FIG. 6 shows a graph
of the cobalt etched in Angstroms as a function of cycles. As shown
in the figure, an etch rate of about 7 Angstroms of cobalt was
removed per cycle, with a 2-cycle incubation. No etch was observed
with either the Br.sub.2 or TMEDA pulses are absent, demonstrating
that neither regent can etch by itself. This example demonstrates
the effectiveness of the etch process, as the cobalt was completely
removed without affecting the underlying SiO.sub.2 substrate. The
process also demonstrated good etch control, with about 7 Angstroms
of cobalt being reliably removed per cycles.
Example 2--Cobalt Etch as a Function of Temperature
[0075] The etch process of Example 1 was repeated, but the
substrate temperature during exposure to Br.sub.2 and TMEDA was
150.degree. C. A possible chemical mechanism of this process is
shown in FIG. 7. A roughening of the surface was observed, but very
little change in terms of Co counts. It is thought that the
reaction is occurring, but that the resulting Co complex is not
volatile at 150.degree. C. This demonstrates that the temperature
must be selected for the specific complexes formed to ensure that
the complex is volatile enough to be able to purge away from the
substrate surface.
[0076] 10 cycles of etch using the same process was measured at
other temperatures, the results of which are shown in FIG. 8. As
seen in the graph, amount of cobalt etched after 10 cycles remained
fairly consistent after the temperature reached 200.degree. C. This
demonstrates that the etch rate is fairly consistent and
independent of temperature once temperature is high enough so that
the resulting cobalt complex is volatile.
Example 3--Cobalt Etch as a Function of Purge Time
[0077] The etch process of Example 1 was repeated twice, but the
substrate temperature during exposure to Br.sub.2 and TMEDA was
200.degree. C. and the purge time was varied from 4 seconds to 2
minutes. FIG. 9 shows a graph of the cobalt etched in Angstroms
versus the number of cycles for a process in which the purge time
was 2 minutes and a process in which the purge time was 4 seconds.
The amount of cobalt etched was nearly identical for the two
processes. This demonstrates that the length of purge time between
cycles does not appear to affect the etch rate of the process.
Example 4--Copper Etch Selectivity
[0078] A copper coupon deposited via PVD and having a thickness of
100-400 Angstroms was provided. The copper coupon overlaid a
tantalum layer overlying a silicon substrate. The cobalt coupon was
exposed to Br.sub.2, followed by treatment with TMEDA at a
temperature of 300.degree. C. A possible chemical mechanism of this
process is shown in FIG. 10. After 10 cycles, all of the copper was
removed from the coupon. After the copper was removed, a shiny
silver was observed on the surface that immediately oxidized and
peeled away from the substrate on exposure to air. This
demonstrates that the copper was completely removed, leaving the
underlying tantalum layer completely untouched, signifying that the
process was selective for copper over tantalum.
* * * * *